50 year old gentleman, a known old CVA patient presented with acute onset right sided weakness. Emergency CT was done to rule out reinfarction.
- Large intracerebral fresh hemorrhage is seen in the left supratentorial parenchyma. Old ischemic changes seen in right cerebral hemisphere.
- Asymmetric subtle hypoattenuation is seen involving the right superior and middle cerebellar peduncles extending into the right cerebellar while matter.
75 year old gentleman, developed acute onset slurring of speech and right sided weakness. Urgent CT brain was done. He was beyond the window period.
- Loss of grey white matter differentiation with hypoattenuation of the left gangliocapsule consistent with acute non hemorrhagic ischemic insult.
- Asymmetric hypoattenuation of right cerebellar white matter. Overlying grey matter appears normal.
Some striking questions these imaging findings raise are:
- Both patients had no clinical presentation with respect to the posterior fossa findings. They presented for clear clinical manifestations pertaining to supratentorial changes.
- These changes did not progress in follow up studies to be florid cerebellar infarctions. In one patient it disappeared, while the other it remained as it is.
- Crossed cerebellar diaschisis has been described from the mid 80s, documented in functional imaging studies as decreased metabolic activity in the contralateral posterior fossa due to a supratentorial pathology.
- It occurs secondary to involvement of the ponto cerebellar fibres and an associated arterial vasoconstriction.
- Sometimes they can result in infarction as well.
- So next time you do see a cerebral hemispheric infarction, go right down to assess the brain stem and contralateral cerebellum. You might just notice this not so uncommon phenomenon.
- Pantano, P., et al. “Crossed cerebellar diaschisis.” Brain 109.4 (1986): 677-694.
- Broich, Karl, et al. “Crossed cerebello-cerebral diaschisis in a patient with cerebellar infarction.” Neuroscience letters 83.1 (1987): 7-12.
- Infeld, Bernard, et al. “Crossed cerebellar diaschisis and brain recovery after stroke.” Stroke 26.1 (1995): 90-95.
- Yamada, Hiroki, et al. “Crossed cerebellar diaschisis: assessment with dynamic susceptibility contrast MR imaging.” Radiology 210.2 (1999): 558-562.